These investigations are directed towards determining the role of dietary copper in cholesterol metabolism using the rat as a model. Dietary copper deficiency produced hypercholesterolemia in rats with associated changes in the cholesterol content of both high and low density lipoproteins. The proposed experiments involved kinetic analysis of tissue cholesterol pools, plasma lecithin cholesterol acyltransferase activity measurements, lipoprotein cholesterol concentrations and arterial cholesterol entry in copper deficient rats.